


UnderCave

by YinYanChan



Category: Undertale (Video Game)
Genre: Alternate Universe - Swapfell (Undertale), Alternate Universe - Underfell (Undertale), Alternate Universe - Underswap (Undertale), Bara Sans, Bara papyrus, Cave Skellies, Doomfanger is sabre cat, F/M, Not a multi universe/alternate universe fic just different tribes of monsters, Swapfell Papyrus (Undertale), Swapfell Sans (Undertale), Underfell Papyrus (Undertale), Underfell Sans (Undertale), Underswap Papyrus (Undertale), Underswap Sans (Undertale), Yes I did picture the cave spongebob meme when I first thought of it... no really it's on my tumblr, cave monsters, lots of miscommunication gonna happen, prehistoric meets today, reader is female, trapped like journey to the center of the earth
Language: English
Status: In-Progress
Published: 2021-02-10
Updated: 2021-02-10
Packaged: 2021-03-16 06:22:21
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,418
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29327739
Author URL: https://archiveofourown.org/users/YinYanChan/pseuds/YinYanChan
Summary: You fell a very long ways from a random hole in the ground while exploring the top of Mt. Ebott. Thanks to climate change there were a few things that the snow and ice had kept hidden... Now suddenly you are in a magical world of dinosuars, Giant prehistoric beasts... and monsters? How are you going to survive and if you do manage to get your wounded leg better... can you even get out?
Relationships: Papyrus (Undertale)/Reader, Sans (Undertale)/Reader
Comments: 16
Kudos: 85





	UnderCave

**Author's Note:**

> I wrote this as a spurt of the moment when I had come up with this idea... I have way to many projects and ideas that I should stop but I can't... Anywho... Enjoy some cave skellies.

Great just great…

Not only did you get lost and fall down a very deep and dark hole… That you knew wasn’t there the last time you had come to Mt. Ebott. The ice and snow had melted considerably over the last few years and you just had to stumble upon a bottomless pit near the very top.

But you’ve come to either the land of the lost or the journey to the center of the earth… Considering how long you fell you’d go with the latter.

There are dinosaurs and other giant creatures of the paleolithic… or were they just monsters?

Tribes of them… all clustered in their own little groups from what you gathered trying to shirk around anything that was a potential threat.

It was a very difficult thing to do considering you took some hefty damage from the fall. Lucky to have survived and had it not been for the twisted vines that acted like a giant springy cushion… you wouldn’t have.

Your leg… although able to put some weight on it… wasn’t doing so good. You’ve got a lot of scratches and a couple deep cuts. So it’s been all you could do to keep moving and never stay in one spot… or become someone or something’s dinner.

You’ve been looking for a good place to hide and defend yourself… ever since you ran across what you thought was a saber tooth tiger… Was a bipedal saber tooth cat? With long gorilla-like arms and a loin cloth… he didn’t appear to give a crap about your presence and continued about his business.

It was still unsettling.

You found a small clearing with it’s own pond with some rock terrain built up around it. Could be a possible cave to hide away in… speaking of a cave… you don’t know how this place was lit up… Or that because of the light underneath it was cold in some spots and warm in others… and bright enough to have dense foliage in certain regions.

This place you found… it seemed to have snow in the higher areas of the built up rocky terrain. You were going to stay below and find a way to heal, eat, and figure a way out of this place… in hopeful safety of a nearby cave.

First thing was first and that was getting some water. The pond was so clear you could see the fish and rocks below. It was a cool refreshing drink. You could see ripples occasionally so it was possible that it wasn’t even stagnant water but connected to an underground spring.

It was also very cold so that nixed the thought of jumping straight in to wash your wounds was out of the question. Yet it might feel good to your aching leg. Trying to find a shallow spot… which water this clear could be misleading in depth.

Stripping your clothes to wade and soak… you noticed bones in the clear water. And an odd skull. Looked almost human but due its shape and teeth it was far from it. It looked rather large and the teeth were shark like but were almost crocodilian how they overlapped the jawline.

At least you wouldn’t be contending with this one as you wade in enough to sit and relax your legs. Let the cool water help with the inflammation and ache of your injured leg. Also wash out your wounds.

Sighing as the cool water laps around your legs and relieving the thrumming pain temporarily. Enjoying it briefly then commence to cleaning your wounds so they won’t fester.

After awhile you started to hear something in the trees nearby… Something big. Pausing you glance around. The noise faded and you sighed in relief. Looking into the water the Skull and bones seem much bigger now as if they were closer but you couldn’t tell.

It was startling enough to make you gasp. Wincing as you flinched back to be reminded that your leg was there to heal.

But… the skull looked so big… much bigger than before… and had it always been facing you?

Paranoid. That’s all this is. You must have a fever so this is a good point to be cleaning those wounds.

You heard a large growl and the cracking of wood in the forest. Close enough to make you launch forward into the water and turn around. The skull is forgotten as you search the woods for a sign of whatever made the noise.

Soon a shadow emerges from the woods you were about to let your guard down only to realize… the sabre cat that came out of the woods was on all fours and not in a loincloth. It was stark black with red eyes. Had a lot of scars on it’s maw.

It was wary about it’s surroundings until its gaze locked on you. It hisses and crouches low.

You were sure it was going to pounce any moment… until you felt the water shift around you and something emerging from the water behind you.

You could feel water dripping down on you as it loomed over you. It startled the big cat to hiss then almost flippantly rear its head back, nose in the air, and walk off.

A deep rumble came from behind you. Turning you shriek at seeing the Skull and bones forming a giant skeleton with vibrant red eyes. It’s gaze intently watching the big cat prance off up the rocky slopes. Water is still gushing from between its teeth. It promptly looks down at you. A tinge of red starts to run across it’s nasal ridge.

It’s maw opens and you are reminded exactly how crocodilian it is… you are about to be eaten by a skeleton!!!!

A barrage of loud grunts and clicks assault your ears.

Is… Is it talking to you? When you don’t seem to respond it tilts it’s skull and somehow narrows it’s sockets at you as if thinking.

Another bit of grunts and clicks yet softer as it takes you all in. Yet you don’t understand and certainly don’t know why you are still in the water with this gigantic living skeleton.

Trying to backpedal failed as your leg decides to fail you this time and you fall back into the water… or you would have had the skeleton not caught you easily and lifted you out of the water… That’s when you realized you were naked and squirmed in its grasp.

It’s taking in your injury… man your leg is bruised but at least your cuts don’t seem as deep as you feared.

Huffing it starts to walk towards the edge and come out of the water with you. Hissing at you as if trying to tell you to be still.

You notice it is wearing a loincloth around it’s pelvis made of luxurious dark fur…. So… It needed a loin cloth? Was it a he?

The skeleton sets you down on a rock and you attempt to hide yourself with no real amount of luck. Using your arms to hide your chest.

“GRRRUSS!!!” It shrieks out startling you. In moments another skeleton rises from the water. What easily could have been a yawn but it was terrifying to behold. A giant lanky skeleton rising out of the deeper depths opening its jaws wide to the sky. Having a slight underbite but had large fangs…. Wait… one of them looked very reminiscent of a long spiral seashell.

It glances over and seems absolutely surprised to see you. The sharp toothed behemoth, that you momentarily forgot, starts another barrage of clicks and grunts at the taller lankier skeleton. This skeleton lumbers out of the water also in a loincloth… This one looked like it would be fluffier around the band had it not been wet. Dark orange but a cream colored fluffy fur band.

Before you knew it this skeleton was leaning its face towards your face. Grunting gently at you but looked somewhat bored.

“I’m sorry? Are you trying to talk to me?” You hope maybe that they might be able to communicate with you.

All you get is them flinching back immediately and bewildered at what came out of your mouth.

Well that dashed that hope.

You did have to giggle at their expression though. You were still trying to get used to the fact that their skull seemed malleable and they actually could close their sockets like eyelids.

Their sockets were blown wide and vacant at first but upon hearing your chuckling those… eyelights? seemed to return very bright and large.

You attempt something.

“Gruss?” You ask pointing at the taller skeleton. Almost forgetting you are naked and promptly trying your best to cover yourself.

He? Perks up. So it must be his name. They could communicate but their language was far more different than yours.

Trying to point to yourself you say your name. Then point back to him and mention his name again.

He seems to understand and the other seems ecstatic. The lights that are his eyes morph into stars.

Another loud barrage of grunts and clicks.

That wicked maw curling into a crocodile grin. He was still gigantic even though hunched slightly.

His arms were slightly longer than proportional. Unlike Gruss this one was thick and stout… he really looked like he could mess someone up given a good reason.

“ACK.” He states placing his hand on his sternum.

Did he just say his name was Ack?

“Ack?” He nods vigorously and you almost feel the vibrations from the hum of approval.

“Gruss, Ack.” Pointing to each as you sound it out. As Ack seems to be preening at this introduction his brother goes to focus on your leg.

Reaching down wrenching it up to get a better look makes you squawk then hiss in pain.

“OW! Stop Gruss! That hurts!” You try smacking his hand away. Yet he doesn’t seem done examining but that doesn’t stop the horrendous pain from him trying to twist and turn it around to get a better view.

Ack smacks at Gruss and growls very low. A growl that made the hair on your arms stand on end.

He drops your leg and it hits the stone you are sitting on.

“OOOOWWWWW!!!!! DAMN IT GRUSS THAT HURT!!!!” Tears cascading down your face as a rush of pain practically immobilizes you. Ack growl is downright feral at this point and he unleashes his furry though higher pitched grunts and clicks.

Yet Gruss seems far more focused on your unveiled chest and splayed form.

“Ah-taa.” He seems in wonder. Sans seems to roll the lights of his eyes in his sockets as if of course.

Out of the bombardment of clicks, growls, and huffs. Ack seems to be scolding Gruss.

Then gestures to you.

“Y/N. AH-TAA.” You were surprised he got your name right at the first go. You just weren’t quite sure what ah-taa was supposed to mean.

Was it because of your condition? Or had Gruss discovered you were female?

Just as the pain seemed to dull you hear another unsettling sound. The Black sabre cat was back and it had a friend.

Another lanky skeleton that’s height could have rivaled Gruss if he wasn’t hunched over that it’s long arms almost served to propel him forward with feline grace himself. His vertebrae were spiked along the ridge of his spine. His fierce maw didn’t have just any teeth… they were spikes of bone jutting from his jaws. 

A very fierce looking skeleton as his expanse claws raked the ground as he hissed at everyone.

The black sabre cat in question looked very proud and smug as it rubbed up against this intimidating skeleton.

Gasping you try to scoot back on the rock.

“DEDGE.” Growled Ack. Both he and Gruss come to stand between you and who you assume is Dedge.

Dedge stands up to his full height then grabs up the sabre cat like it was a kitten and pets it. You now notice he has a more leather like loin cloth. He then sets the cat down.

“ANG.” He yells at the cat then shoos it away… was the cat named Ang?

Then Dedge approaches and he seems very hostile.

So focused on him you didn’t sense the looming creature behind you. Until you were snatched up making you shriek.

You are turned to face another skeleton!? This one was just as bulky as Ack and had similar teeth but had a big underbite… in fact a tooth was missing and it looked like an arrowhead had been shoved in its place.

Leering Red eyes as he turned you around and seemed to like what he was seeing. Was wearing a leathery loincloth as well but he had tufts of fluffy yellow fur around the band.

You hear both Gruss and Ack growl fiercely at the newcomer.

“RECK!!!” Ack yells out before unleashing more growls and huffs… you did notice no clicks this time.

Yet this Reck doesn’t seem to be paying attention to them. His lecherous grin unnerves you.

“Dedge! Ah-taa!” Reck snickers holding you up for Dedge to see better.

Then you watch as this fierce skeleton looks up at you then his face flushes red with apparent shock written all over it.

“A-AH-TAA?” Dedge looks you over and there isn’t anyway to hide that you are obviously female from the way Reck is holding you.

This is getting to be a bit much and not to mention you are still in pain. Ack seems to be the one to call out to as he did seem concerned.

“Ack! Help!” You reach out to him and it’s over in the blink of an eye.

You are in Ack’s strong but very gentle arms and his foot has connected right between the eye sockets of Reck.

As Reck hisses and growls holding his head… Ack is gently cooing you as Gruss fends off the agitated Dedge.

Gruss is quick to dodge a swipe from Dedge’s massive claws. Then somehow takes a deep breath.

“Ans! Appy! Boo! Etch!” He shouts towards the sky and lets it echo. Dedge freezes and growls. Reck just grunts and growls at Gruss with a thoroughly annoyed look.

Why do you get the feeling these aren’t the only skeletons around? Ack nuzzles you and keeps you in surprising comfort in his warm embrace.

You hear the twisting of wood and bark as very large things are heading your way.

**Author's Note:**

> Swapfell Sans: Ack  
> Swapfell Papyrus: Gruss  
> Underfell Papyrus: Dedge  
> Underfell Sans: Reck  
> Underswap Sans: Boo  
> Underswap Papyrus: Etch  
> Undertale Sans: Ans  
> Undertale Papyrus: Appy  
> Doomfanger: Ang


End file.
